Three-phase chains are the most widespread in modern power, they give the chance to receive on one installation two operational tension — linear and phase.
Linear call tension between two phase wires, sometimes mention it as interphase or interphase. Tension between a zero wire and one of phase is considered phase. In normal service conditions linear tension is identical and surpasses phase by 1.73 times.
Operational tension of a three-phase chain
Three-phase chains have a number of advantages in comparison with multiphase and single-phase, with their help it is possible to receive easily rotary circular magnetic field which ensures functioning of asynchronous engines. Tension of a three-phase chain is estimated on its linear tension, for the lines departing from substations it is established by 380 V what corresponds to phase tension in 220 V. For designation of rated voltage of three-phase four-wire network use both sizes — 380/220 V, emphasizing with it that not only the three-phase devices calculated on the rated voltage of 380 V but also single-phase — on 220 V can be connected to it.
Phase call the part of a multiphase system having identical characteristic of current. Regardless of a way of connection of phases exist three identical on the operating value of tension of a three-phase chain. They are shifted rather each other on a phase on the corner making 2π/3. The four-wire chain, besides three linear tension, has also three phase.
Rated voltage
The most widespread rated voltage of receivers of alternating current are 220, 127 and 380 V. Tension of 220 and 380 V is most often used for power supply of industrial devices, and 127 and 220 V — for household. All of them (127, 220 and 380 V) are considered as rated voltage of three-phase network. Their existence in four-wire network gives the chance to connect single-phase receivers which are calculated on 220 and 127 V or 380 and 220 V.
Distinctions of electrical distribution systems
The greatest distribution was received by the three-phase system of 380/220 V with the grounded neutral, however other ways of power distribution meet. For example, in a number of settlements it is possible to find a three-phase system with the ungrounded isolated neutral and linear voltage of 220 V. In this case the zero wire is not required, and defeat probability electric current at violation of isolation decreases at the expense of an ungrounded neutral. Three-phase receivers are connected to three phase wires, and single-phase — on linear tension between any couple of phase wires.